Pope Francis has vowed the Catholic church will “never again” cover up clerical sexual abuse and demanded that priests who raped and abused children turn themselves in.

The pontiff dedicated his Christmas speech to the Vatican bureaucracy to the theme of abuse, after a year of revelations of sexual misconduct and cover-ups that rocked his papacy and caused a crisis of confidence in the Catholic hierarchy.

He acknowledged the church had not always treated the issue seriously, blaming leaders who out of inexperience or shortsightedness acted “irresponsibly” by refusing to believe victims. But he said the church would never again conceal or dismiss such cases.

“Let it be clear that before these abominations, the church will spare no effort to do all that is necessary to bring to justice whosoever has committed such crimes,” he said.

The pope urged victims to come forward, thanked the media for giving them a voice and issued a stark warning to abusers: “Convert and hand yourself over to human justice, and prepare for divine justice.”

His remarks capped a difficult year for the Catholic church, which began with the pontiff’s botched handling of a sexual abuse scandal in Chile and ended with US state prosecutors uncovering decades of cover-ups.

The pope has summoned church leaders from around the world to an abuse prevention summit in February, indicating that he has come to realise the problem is far greater and more widespread than he had understood at the start of his pontificate five years ago.

His demand that abusers turn themselves in to face “human justice” was significant, and echoed his previous calls for mafia bosses and corrupt politicians to convert.

Vatican guidelines ask bishops to report priestly abusers to police in countries where the law requires it – a technicality that survivors and their advocates have long claimed was an attempt by the church to avoid its moral obligation to protect children.

The pope told the Vatican bureaucrats who run the 1.2 billion-member church that the scandal undermined the credibility of the entire Catholic enterprise, and that they must embark on a “path of purification”.

He prayed for help for the church to discern true cases from false ones. “This is no easy task, since the guilty are capable of skilfully covering their tracks” and choosing victims who will keep silent, he said.

It was perhaps a veiled reference to Theodore McCarrick, the disgraced former archbishop of Washington, who faces a canonical trial on allegations that he groped a teenage altar boy in the 1970s.

The McCarrick revelations have fuelled a crisis of confidence in the US and Vatican hierarchy amid allegations that it was an open secret that he sexually abused seminarians, but nevertheless was allowed to rise to power.

The pope has used previous Christmas greetings to criticise the failings of the curia – the administrative unit of the Holy See – accusing it of “spiritual Alzheimer’s” disease and taking part in the “terrorism of gossip”.

His remarks this year had a more global outlook, claiming there were priests who, “without batting an eye”, were ready to enter into a “web of corruption” by abusing those in their care.